This invention relates generally to switching amplifiers and, in particular, to apparatus and methods for providing amplifier output voltages in excess of the available power supply.
Typical switching amplifiers are comprised of multiple switching devices modulating connection between one or more power supplies and a load impedance. Resultantly, such circuit configurations are unable to provide voltages to the load in excess of that provided by the associated power supplies.
In limited-voltage situations, system losses often circumvent the use of low-impedance loads necessary to transfer large amounts of power. For such situations, there exists a need for a simple and inexpensive technique for providing amplifier output voltages in excess of the available power supply.
The present invention resides in a method and apparatus facilitating a voltage multiplication into the output stage of a switching amplifier. Broadly, a plurality of switching devices are used to modulate the interconnection between a power supply, a reactance and a load in accordance with a modulation signal, such that the voltage across the load exceeds the supply voltage. In the situation where the reactance is a capacitor, the voltage across the load exceeds the supply voltage by two or an integer multiple thereof.
In the preferred embodiment, a pair of reactances and attendant switching devices are used to modulate the interconnection between the supply voltage relative to both sides of the load depending upon the sign of the modulation signal.